Simplify the following expression: $3\sqrt{117}$.
Solution: First, try to factor a perfect square out of the radical. $= 3\sqrt{117}$ $= 3\sqrt{9 \cdot 13}$ Separate the radical and simplify. $= 3\sqrt{9} \cdot \sqrt{13}$ $= 3 \cdot 3 \cdot \sqrt{13}$ $= 9\sqrt{13}$